From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: PV drivers on HVM using Xen 4.1.1 Date: Thu, 27 Oct 2011 09:35:37 -0400 Message-ID: <20111027133536.GD2242@phenom.dumpdata.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Alex Bligh Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On Thu, Oct 27, 2011 at 01:56:41PM +0100, Alex Bligh wrote: > I think I've found one reason why we can't get PV block drivers on HVM > domUs working on Xen 4.1.1 - whether we use a pvops or a xenlinux > domU kernel. > > We are using a line like: > > disk = [ "tap:aio:/tmp/centos-pvd.img,xvda,w" ] > > We are using effectively a standard 3.0 kernel. Config options including > the word XEN are below. > > We do not see blktapctrl starting in Xen 4.1.1 dom0, but it does > start in Xen3. In fact as far as I can tell the Ubuntu Xen4 package > does not contain blktapctrl at all (which would explain why it doesn't > start). Do we need this? > > It has been suggested that we don't need this, but we do need a kernel > module that provides blktap. > > http://www.vr.org/knowledgebase/1112/Xen-Paravirt-Ops.html > > suggests these might be queued for the non-existent "2.6.40", but > it's suggested these aren't in 3.0. Right, they are a no-go. There is a > > http://wiki.xensource.com/xenwiki/XAPI_on_debian > > suggests there are dmks modules available, but that blktap is currenly > only 32 bit. Can that be correct? There is a 64-bit (and 32-bit) version on Daniel's git tree: git://xenbits.xensource.com/people/dstodden/linux.git .. but the deal is that it is unmaintained (Daniel left Citrix). Thought interestingly .. he made a version of it where all of the fiddling with the generic code has been removed. Neat. > > Isn't this what blkback does? Blkback can't handle files - it can only handle block devices. > > domU config is below. Note the very same VM with the same config file > works just fine on xen 3.3.1. This domU is Centos 2.6.18 with > unmodified_drivers xenlinux type kernel (as supplied by Centos). Every > other kernel we've tried does the same, save that modern ones also > unplug the emulated devices so no disks appear as well. > > PV nics work fine.